Computer input devices for entering commands into a computer are well known and currently available in a variety of configurations. Many such input devices include a rotatable ball mounted to the base of the device. As the ball is moved relative to the base, transducers sense the movement of the ball and generate signals indicative of the direction and amount of that movement. The signals are used, for example, to control movement of a cursor on the screen of a computer.
A type of input device known as a "mouse," houses the rotatable ball so that it extends from the underside to frictionally engage a work surface, such as a desktop. The movement of the mouse along the work surface causes rotation of the ball for generating the signals that are converted to cursor movement on the computer screen. A trackball-type input device, on the other hand, has its rotatable ball exposed for manipulation by the user's finger(s) and/or thumb. Similar ball-position signals are generated.
Computer input devices also include keys. Depressing one of the keys changes the state of an associated switch, which permits a user to enter various commands into the computer. The nature of the command usually depends upon the position of the cursor on the screen.
One mouse-type pointing device, available from Microsoft Corporation under the trademark IntelliMouse, includes a roller or wheel that protrudes from the top of the device and is coupled to a transducer for producing a signal indicating the rotation of the wheel. That signal may be used, for example, for scrolling through a window displayed on a computer, which function was heretofore performed by moving the cursor to the window "scroll bar" and depressing a key as needed to scroll through whatever is displayed in the window. For convenience, the wheel will be hereafter referred to as a "scrolling wheel." The keys, trackball, and scrolling wheel may be collectively referred to as the actuators carried on the input device.
Irrespective of the type of input device employed, mouse or trackball, it is important that the device be comfortable for the user to operate, especially over long periods of time. Such comfort is obtained by careful attention to ergonomic factors, particularly toward minimizing stress in the user's fingers, wrist, and forearm. Providing a comfortable computer input device can be especially challenging when one's design goal includes enhancing the function of the device over what went before, such as by combining, along with keys and a trackball, an actuator like the aforementioned scrolling wheel.
The present invention is directed to an ergonomic input device that comfortably supports the hand of the user while the wrist is minimally extended and the thumb and fingers are oriented in neutral postures for operation of the actuators carried on the device. The overall configuration of the device and the arrangement of these actuators permits the user to carry out all of the functions provided by the actuators while the forearm is in a neutral posture zone, between pronation and supination of the forearm.
More particulary, the base of the device is shaped so that the metacarpal-phalangeal joint ridge is supported, as is the remainder of the user's palm. In this regard, the palm is considered here to comprise the metacarpal-phalangeal joint ridge (which, for the present, can be thought of as the area where the fingers are jointed to the end of the palm), the thenar eminence (the mound of the palm at the base of the thumb), and the central region of the palm that defines what is known as the palm gutter.
The size and shape of the device is such that a wide range of hand sizes will be comfortably supported in using the device, including those hand sizes falling within a range defined by the fifth percentile female (small hand) to the ninety-fifth percentile male (large hand) of North American adults.
The actuator arrangements and shape of the device also minimizes extension of the wrist and fingers. Abduction and adduction of the fingers is also minimized.
Moreover, the actuators are located such that the primary actuator (trackball) is oriented for manipulation by the finger with the greatest dexterity; namely, the index finger. Secondary functions, such as depressing the keys "clicking") and operating the scrolling wheel are assigned to the slightly less dextrous digits, the thumb and middle finger, respectively. The even less-dextrous ring finger and little finger are not associated with any actuators but are instead comfortably supported by the base of the device, in a manner that facilitates a comfortable overall grip or feel of the device and act as resistance to button activation force vectors by the thumb.
The foregoing and other features and advantages of the preferred embodiments of the present invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.